Android中canvas常用方法
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在自定义VIew中经常使用到Canvas对象的方法:
1 绘制点:
public void drawPoint(float x, float y, Paint paint)
x:表示x轴方法的坐标
y:表示y轴方法的坐标 这坐标是相对于它的父view,而不是屏幕
paint:表示你所画点用到的画笔
public void drawPoints(float[] pts,Paint paint) 绘制多个点
pts:是一个float数组,存储的是点的集合
public void drawPoints(float[] pts, int offset, int count,Paint paint)
pts:是一个float数组,存储的是点的集合
offset:集合中跳过的数值个数
count:参与绘制的数值的个数
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#00ffff")); paint.setStrokeWidth(20); canvas.drawPoint(100, 50, paint); float[] point = {50, 150, 150, 150, 250, 150}; canvas.drawPoints(point, paint); float[] points = {50, 250, 150, 250, 250, 250, 350, 250, 450, 250}; canvas.drawPoints(points, 4, 4, paint); }
2 绘制线
public void drawLine(float startX, float startY, float stopX, float stopY,Paint paint)
startX:第一个点的起始x轴坐标
startY:第一个点的起始y轴坐标
stopX:结束点x轴坐标
stopY:结束点y轴坐标
paint:绘制线所用到的画笔
画多条线
public void drawLines(float[] pts, Paint paint)
pts:drawPoints中的参数是同一意思
public void drawLines(float[] pts, int offset, int count, Paint paint)
pts:同上
offset:和drawPoints是一样
count:和drawPoints是一样
paint:同上
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#456456")); paint.setStrokeWidth(20); canvas.drawLine(600, 100, 800, 300, paint); float[] lines = {600, 200, 800, 400, 600, 300, 800, 500}; canvas.drawLines(lines, paint); float[] pts = {100,100,400,100,400,100,400,400,400,400,100,400,100,400,100,100}; canvas.drawLines(pts,4,12,paint); }
3 绘制矩形
public void drawRect(float left, float top, float right, float bottom, Paint paint)
left:第一个点距离x轴的距离(单位像素)
top:第一个点距离y轴的距离
right:第二个距离x轴的距离
bottom:第二个点距离y轴的距离
Rect和RectF用法上没什么差别,RectF相比Rect精度更准确
public void drawRect(Rect r, Paint paint)
r就是上面2个点封装成了一个矩形而已。
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#567354")); paint.setStrokeWidth(20); canvas.drawRect(100,100,400,400,paint); Rect rect = new Rect(500,100,600,400); canvas.drawRect(rect,paint); }
4 绘制圆角矩形
public void drawRoundRect(float left, float top, float right, float bottom, float rx, float ry,Paint paint)
left 第一个点x轴方向距离(像素)
top:第一个点y轴方向距离
right:第二个点x轴方向距离
bottom:第二个点y轴方向距离
rx:生成圆角椭圆的x轴半径
ry:生成圆角椭圆的y轴半径
paint:绘制圆角矩形所需的画笔
@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint.setColor(Color.RED); mPaint.setStrokeWidth(10); mPaint.setStyle(Paint.Style.STROKE); canvas.drawRoundRect(100f,100f,600f,600f,20f,20f,mPaint);}
5 绘制圆
public void drawCircle(float cx, float cy, float radius,Paint paint)
cx:圆心x轴方向距离
cy:圆心y轴方向距离
radius:圆的半径
paint:绘制圆所需的画笔
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint1 = new Paint(); paint.setColor(Color.parseColor("#a23d46")); paint.setStrokeWidth(2); paint1.setStyle(Paint.Style.STROKE); paint1.setStrokeWidth(2); canvas.drawCircle(200,200,150,paint); canvas.drawCircle(600,200,150,paint1); }
6 绘制椭圆
椭圆是根据矩形里面的内切圆就是依赖外面的矩形而形成的
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#a23d46")); paint.setStrokeWidth(2); RectF rect = new RectF(200,200,600,500); canvas.drawRect(rect,paint); paint.setColor(Color.GRAY); canvas.drawOval(rect,paint); }
7 绘制弧
弧是根据椭圆来定的,椭圆是根据矩形来定的
public void drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter,Paint paint)
oval:绘制弧所依赖的矩形
startAngle:弧开始的角度,以X轴正方向为0度
sweepAngle:弧持续的角度
useCenter:是否有弧的两边,True,还两边,False,只有一条弧
@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint.setColor(Color.RED); mPaint.setStrokeWidth(10); mPaint.setStyle(Paint.Style.STROKE); RectF rect = new RectF(100,100,500,400); canvas.drawArc(rect,0,90,true,mPaint);}
如果把第四个参数传false
@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint.setColor(Color.RED); mPaint.setStrokeWidth(10); mPaint.setStyle(Paint.Style.STROKE); RectF rect = new RectF(100,100,500,400); canvas.drawRect(rect,mPaint); mPaint.setColor(Color.BLUE); canvas.drawOval(rect,mPaint); mPaint.setColor(Color.YELLOW); canvas.drawArc(rect,0,90,true,mPaint);}
现在看到我们绘制的矩形,我们从中可以得出它的坐标点为圆心点,现在我把弧所持续的角度为-90
@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint.setColor(Color.RED); mPaint.setStrokeWidth(10); mPaint.setStyle(Paint.Style.STROKE); RectF rect = new RectF(100,100,500,400); canvas.drawRect(rect,mPaint); mPaint.setColor(Color.BLUE); canvas.drawOval(rect,mPaint); mPaint.setColor(Color.YELLOW); canvas.drawArc(rect,0,-90,true,mPaint);}
发现当所持续的角度为-90度是逆时针转90的,从这可以得出一个简单的结论:当所持续的角度为正数是顺时针,当所持续的角度为负数时,是逆时针,
现在还有一个参数startAngle就是弧开始的角度,之前是传入0,现在改为90,
@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint.setColor(Color.RED); mPaint.setStrokeWidth(10); mPaint.setStyle(Paint.Style.STROKE); RectF rect = new RectF(100,100,500,400); canvas.drawRect(rect,mPaint); mPaint.setColor(Color.BLUE); canvas.drawOval(rect,mPaint); mPaint.setColor(Color.YELLOW); canvas.drawArc(rect,90,-90,true,mPaint);}
现在画图来解释上面第二个和第三个参数如下图:
8 绘制多边形
public void drawPath(Path path, Paint paint)
path:路径
paint:所画路径需要的画笔
@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#987452")); paint.setStrokeWidth(2); Path path = new Path(); path.moveTo(100,100); path.lineTo(100,300); path.lineTo(500,300); path.close(); canvas.drawPath(path,paint);}
moveTo()方法是绘制多边形的起点,lineTo()是连接上一个点,构成一条线,path的close()方法一定要记得调用,close()能保证多边形构成的线能闭合,
add()的使用
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#987452")); paint.setStrokeWidth(6); paint.setStyle(Paint.Style.STROKE); Path path = new Path(); path.moveTo(100,100); path.lineTo(100,300); path.lineTo(500,300); path.close(); path.addCircle(100,160,30, Path.Direction.CW); canvas.drawPath(path,paint); }
9 绘制带文字的多边形
public void drawTextOnPath(String text,Path path, float hOffset,float vOffset,Paint paint)
text:绘制到path上的文字
path:路径
float hOffset : 与路径起始点的水平偏移距离
float vOffset : 与路径中心的垂直偏移量
paint:同上
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#987452")); paint.setStrokeWidth(2); paint.setStyle(Paint.Style.STROKE); String text="你们好啊 地球人"; Path path = new Path(); Path path1 = new Path(); path.addCircle(300,300,200, Path.Direction.CCW); path1.addCircle(800,300,200, Path.Direction.CCW); canvas.drawPath(path,paint); canvas.drawPath(path1,paint); paint.setTextSize(50);//设置字体 paint.setColor(Color.GREEN); paint.setAntiAlias(true); canvas.drawTextOnPath(text,path,0,0,paint); canvas.drawTextOnPath(text,path1,10,10,paint); }
分析图:
path.addCircle(300,300,200, Path.Direction.CCW);方法的第四个参数讲下,
Path.Direction有两个值:
Path.Direction.CCW:是counter-clockwise缩写,指创建逆时针方向的矩形路径;
Path.Direction.CW:是clockwise的缩写,指创建顺时针方向的矩形路径
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#987452")); paint.setStrokeWidth(2); paint.setStyle(Paint.Style.STROKE); String text="你们好啊 地球人"; Path path = new Path(); Path path1 = new Path(); path.addCircle(300,300,200, Path.Direction.CW); path1.addCircle(800,300,200, Path.Direction.CCW); canvas.drawPath(path,paint); canvas.drawPath(path1,paint); paint.setTextSize(50);//设置字体 paint.setColor(Color.GREEN); paint.setAntiAlias(true); canvas.drawTextOnPath(text,path,0,0,paint); canvas.drawTextOnPath(text,path1,10,10,paint); }
10 绘制文字
这里就不讲drawText()了,在讲Paint中这个讲的比较详细,可以去看看那个博客,绘制文字讲的是这个方法
public void drawPosText(char[] text, int index, int count,float[] pos,Paint paint)
参数说明:
text:所绘制文字的数组
index:从第几个数组小标位置开始绘制
count:绘制多少文字
paint:同上
pos:是所绘制所在位置的坐标的集合
@Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); paint = new Paint(); paint.setColor(Color.parseColor("#146ad4")); paint.setStrokeWidth(2); paint.setTextSize(50); paint.setStyle(Paint.Style.STROKE); float[] pos = new float[]{140, 200, 200, 300, 320, 400, 440, 500}; char[] text = {'北', '京', '你', '好'}; canvas.drawPosText(text, 0, 4, pos, paint); }
实现一个轨迹或者涂鸦功能
public class All_View extends View { private Paint mPaint; private Path mPath; public All_View(Context context) { this(context, null); } public All_View(Context context, AttributeSet attrs) { this(context, attrs, 0); } public All_View(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); mPaint = new Paint(); mPath = new Path(); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint.setColor(Color.RED); mPaint.setStrokeWidth(5); mPaint.setTextSize(60); mPaint.setStyle(Paint.Style.STROKE); canvas.drawPath(mPath, mPaint); } @Override public boolean onTouchEvent(MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: mPath.moveTo(event.getX(), event.getY()); return true; case MotionEvent.ACTION_MOVE: mPath.lineTo(event.getX(), event.getY()); invalidate(); break; case MotionEvent.ACTION_UP: break; } return super.onTouchEvent(event); }}
参考:http://blog.csdn.net/coderinchina/article/details/51442075
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